Hormonal influence on the secretory immune system of the eye: endocrine interactions in the control of IgA and secretory component levels in tears of rats.

Previous research from our laboratory has demonstrated that androgens regulate the ocular secretory immune system of the rat. The purpose of the present study was to determine whether other hormones might influence this androgen effect. Experiments involved the daily administration of saline or hormones to adult orchiectomized rats, the collection of tears 24 hr after the fourth hormone injection, and the measurement of free secretory component (SC), IgA and total protein levels in tears. Our first aim was to evaluate whether female sex steroids might antagonize androgen action on tear IgA and SC: orchiectomized rats were treated with combinations of saline, testosterone, oestradiol or progesterone. Testosterone induced a significant increase in the tear SC and IgA concentrations, as compared to those of saline-injected controls. This androgen effect was not inhibited by co-treatment with oestradiol or progesterone, nor duplicated by the administration of these hormones alone. Our second aim was to assess whether the absence of certain hormones might alter tear SC and IgA levels, or influence the ocular response to androgen exposure: rats underwent orchiectomies and specific endocrine organ ablations or appropriate sham-surgery. Absence of the pituitary gland, but not the thyroid, adrenal or pineal glands, resulted in a significant decrease in tear SC, IgA and total protein content. In addition, removal of the thyroid or adrenal glands did not prevent the testosterone-associated increase in tear SC and IgA, although thyroidectomy or adrenalectomy did diminish the magnitude of the androgen response. In contrast, hypophysectomy completely blocked the effect of testosterone on both tear SC and IgA. These results indicate that the hypothalamic-pituitary axis may regulate, or mediate, the action of androgens on ocular immunity in the rat.